He now sees that time as a turning point in his career, as he stands on verge of winning a maiden Tour de France title and becoming just the sixth man to win all of cycling's three major races.
In 2008, the International Cycling Union (UCI) became the first international sport federation to implement the biological passport, which creates a blood profile for riders and helps detect doping.
Nibali finished the 2008 Tour in 19th position overall, but just two years later he went on to win the Vuelta a Espana.
It was the biological passport that helped level the playing field, according to Nibali, who, at that time, had called for cheats to be locked up.
"It is true that in 2008, I felt a bit sad and disappointed. I wanted the white jersey (for the best under-25 rider)," Nibali, who is poised to become the first Italian since Marco Pantani in 1998 to win the Tour, told a news conference on Saturday.
He leads Frenchman Jean-Christophe Peraud by 7 minutes and 52 seconds going into the Tour's final stage on Sunday, a procession to the Champs Elysees in Paris.
"A lot of progress has been made and we can see the results now," said Nibali.
"If there had not been all these controls, targeted controls, the biological passport, maybe I would not be here," he added.
Asked if he would be ready to have his samples stored for future testing, Nibali replied: "Yes, I'm ready to accept this idea."
Some pundits have argued that Nibali's title will lack credibility after last year's winner Chris Froome and twice champion Alberto Contador, the two pre-race favourites, dropped out following crashes.
The 29-year-old Sicilian, however, hit back that crashes are part of the race and that he already had a lead of 2:37 when Spain's Contador dropped out.
Yet he is looking forward to next year and the chance to challenge those who either crashed out or missed this year's event.
"It will be a good battle with Contador, Froome, and (Nairo) Quintana," he said.
Colombian Quintana skipped the Tour this year to focus on the Giro d'Italia, which he won.
Nibali made the same choice last year, adding the Giro, to his 2010 Vuelta title.
When his Tour victory is confirmed on Sunday, he will join Contador, Frenchmen Bernard Hinault and Jacques Anquetil, Italian Felice Gimondi and Belgian Eddy Merckx as the only men to have won all three grand tours.
- Sports & Recreation
- International Cycling Union
- biological passport
- Alberto Contador